Designing Dam Upgrades and Protecting Wetlands
Aspetuck Reservoir Dam is an approximately 700-LF-long, 11-LF-high earth embankment water supply dam with a 500 LF concrete ogee spillway. The dam was constructed in 1913 and is used to transfer water from the Saugatuck Reservoir to the Hemlocks Reservoir, both of which provide drinking water to the greater Bridgeport, CT area. Aspetuck Reservoir Dam is a small size, Significant Hazard dam as determined by the Connecticut Department of Energy and Environmental Protection (CT DEEP) Dam Safety Program.
Tighe & Bond completed a visual inspection and alternatives analysis to evaluate repair approaches for the observed deficiencies. Following the visual inspection, wetland delineations and a wetlands functions and values assessment was conducted to support the alternatives analysis, design, and permitting. Tighe & Bond attended pre-application meetings with regulatory staff and fisheries to review the design approach for adding eel passage improvements to the dam as part of the rehabilitation project.
A hydraulic and hydrologic evaluation was also performed to determine whether the dam had adequate hydraulic capacity to pass the 500-year storm event. The project design included phased construction that isolated segments of the spillway and other dam components for repair while maintaining downstream flows and the operation of Aquarion Water Company’s water supply system. The phased construction approach was also designed to minimize impacts to downstream wetlands and to isolate construction activities from open water.
Tighe & Bond designed the proposed improvements prepared permit applications for a Pre-Construction Notification, 401 Water Quality Certificate, and Dam Safety Permit. The permit review process included coordination with CT DEEP fisheries and the Natural Diversity Database program. Tighe & Bond provided construction administration and construction observation services for the project, which included both engineering and compliance with the conditions of the environmental permits.